In the packaging of beverages and solid or semi-solid food products it is quite desirable, for reasons of sanitation, to close the container by means which will be permanently deformed or disfigured upon the first opening of the container to provide a readily apparent indication that the container has been opened, such closures commonly being referred to as tamperproof closures. Among the more popular types of tamperproof closures used in the trade are the single element, rolled on metallic closures which are applied to the threaded neck portions of glass containers and which have their inwardly projecting mating threads rolled against the glass neck by external tooling. However, such closures may not readily be applied to wide-mouth containers formed from relatively thin materials, such as nestable paper containers or nestable thermoformed plastic containers, because such containers are not ordinarily provided with a threaded portion, and because the mouths of such containers, because of their large size and the thinness of the surrounding walls, would not withstand the magnitude of the forces required to deform portions of the skirt of a metallic closure by rolling in place. Also, such closures are generally of a non-nestable configuration, and large numbers thereof, especially in wide-mouth sizes would occupy large volumes of space during shipment and storage.
Another known type of tamperproof closuring concept, which is applicable to wide-mouth containers or to containers formed with relatively non-rigid mouths, involves the use of a pair of separate elements, a closure element, generally of non-nestable configuration, with an outwardly projecting bead or flange at the bottom or the skirt thereof and a band formed from an elastic or heat-shrinkable material which is separately inserted over the mouth of the closed container to securely engage the flange or bead of the closure. Such a closuring concept, however, may not readily be applied to the nestable paper or thermoformed plastic containers which have been widely used for many years in the packaging of dairy products such as ice-cream, cottage cheese, yogurt or the like, as existing types of container filling and closing machines are not equipped to mechanically perform the extra step of affixing a tamperproof band to a previously closed container.